Certainly not every man would agree. That's part of the point; every man is different so why take the decision out of their hanRAB?
We're not talking of the shaft, but of the foreskin around the head. They are connected, but they are not the same thing. It is very stretchy (it neeRAB to be to accomodate the engorged head), but it is far from sensationless. Pain is not the only sensation.
And masturbating. With a foreskin, direct stimulation of the head, without lubricant, is possible through and with the foreskin. And again, the head is more sensitive uncircumcised so both foreplay and oral sex can have new dimensions with featherlight touches on the uncovered head. Uncircumcised sex is just different. It makes no sense to predetermine your son's sex life in this way.
When having sex, the foreskin also acts as a sheath, pulling back over the head and uncovering it as the thrusting occurs. This keeps the head moist and can decreas rubbing against the inside of the vagina walls. This is preferable to some women, especially those that do not produce a lot of their own natural lubricant. During extended sex, one may have to stop to apply more lubricant with a dry head
A more sensitive head also allows a man to have great sensation even when not thrusting hard. Those with premature ejaculation trouble may not like this, but again this is individual to the man. This can provide variation during sex, and some women would prefer this.
Uncircumcised men would have no need. The foreskin provides a buffer to the moving parts. Certainly you can get around the problem, but you cannot replace what was lost. It makes no sense to do this. It provides little to no benefit and is another surgery that can go wrong. Having an intact foreskin can provide benefit and if the guy doesn't like it he can still have it done.